the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Jan 2026
Evidence for subglacial flooding in labyrinthine channels on Devon Island, Nunavut, Canada
Abstract. Subglacial drainage systems route glacial meltwater to the ice margin either via efficient, channelized systems or inefficient, distributed systems. The interplay between channelized and distributed drainage systems varies spatially and temporally, governed by meltwater supply and abundance, bed roughness and topography, ice sliding velocity, and ice driving stress. Subglacial channel formation and evolution are therefore affected by variability in meltwater supply to subglacial conduits, and these changes may be recorded in the geomorphology of these channels. The formation of subglacial bedrock channels is attributed to higher energy and/or higher magnitude discharge events, such as the episodic release of meltwater in the form of either subglacial or proglacial floods, in comparison to the energy or discharge required to excavate channels in soft sediment. Common features of landscapes modified by meltwater floods include anastomosing channels and multiple erosive surfaces, wherein the pre-existing drainage system is inundated, resulting in the incision of new channels that reconnect downstream. Devon Island in the Canadian Arctic Archipelago was covered by the thin (<1000 m), cold-to-polythermal based Innuitian Ice Sheet over the course of at least three glacial expansions during the last glacial cycle. Despite this, there is a conspicuous lack of typical glacial landforms, and instead, the inland plateau region of the island is incised by ubiquitous subglacial and lateral meltwater channels. Some sets of bedrock subglacial channels on Devon Island bear a striking resemblance to the morphology of The Labyrinth in Antarctica, which formed by the episodic drainage of a subglacial lake. The characteristics, topology, and morphology of these channels, referred to as 'Labyrinthine channels' hereafter, together with two subglacial channel networks make the focus of this study. We argue that, within both labyrinthine and other subglacial channel networks on Devon Island, the presence of distinct erosional surfaces, anastomosing channels, and profile slope breaks imply formation by short-lived locally intense episodes of erosion. The presence of well-defined erosional surfaces suggests floods progressively incised into lower elevations where meltwater was captured by pre-existing or incipient channels. Moreover, steep contacts between erosional surfaces, termed here as "slope breaks", are similar to fluvial knickpoints and hanging valleys found in other notable landscapes caused by flooding, such as the Channeled Scablands, possibly indicating channel headward erosion in response to pulses of intense erosion. Overall, we suggest that the presence of discrete erosional surfaces implies multiple flooding events, and that changing flow conditions during these events are evidenced by slope breaks. Multiple erosional surfaces, scabland-type landscapes, anastomosing bedrock channels, and hanging valleys with steep slope breaks are not consistent with ice marginal melt, demanding large discharge conditions and pulses of activity, and pointing at subglacial rather than marginal or proglacial environments of formation. This work aids in enhancing the current understanding of the role and dynamics of meltwater drainage systems operating under the cold-to-polythermal based Innuitian Ice Sheet, perhaps shedding light into its retreat dynamics, and bolstering the interpretation of glacial dynamics on Devon Island.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-5667', Anonymous Referee #1, 18 Feb 2026
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AC1: 'Reply on RC1', Simona Ruso, 03 Apr 2026
Dear Referee #1,
We thank you for your insightful and helpful comments of our manuscript that will enhance the quality of our work. The following is a line-by-line response to your Referee Comments.
Major comments
- Map also at least one lateral meltwater channels system to better distinguish between ice-marginal vs subglacial channels. Are they morphologically the same as modern ice marginal channels forming around the ice cap? Do penultimate marginal channels become subsequent subglacial channels?
To address Reviewer #1’s suggestion to map the lateral meltwater channels we will include a figure composed of an image of lateral meltwater channels taken in the field in 2024 next to the ArcticDEM of the same channels, so that readers can visualize the morphology and distinctive characteristics (outlined in lines 119-129) of the channel types. This figure will be included in supplementary information with this article and referred to in lines 119 – 129. We agree that a direct comparison would be interesting, however, this would require another field season, which is beyond the scope of this paper. As the reviewer points out, we acknowledge that these channels could have formed over different glacial cycles, seeing influences of subglacial, ice marginal, and paraglacial processes through the Quaternary. Without a precise chronology (Andres Escorihuela et al., in preparation), we cannot pinpoint the possible imprint of past glacial cycles in these networks. However, two aspects indicate synchronous activity in the whole of the network, which plays against the lateral meltwater channel hypothesis: First, the labyrinthine, anastomosing morphology described to have formed through channel overflow. Next, both the regular spacing between the channel heads at the different networks (notably SG1, SG2, SG3) and their precise alignment suggest synchronous emplacement during the self-organization of the subglacial channelized drainage system (e.g., Schoof, 2010, supplementary information). Hence, we believe based on the planform morphology that the channels within each network likely formed at the same time and were therefore not initially marginal channels that were reused as subglacial pathways. We believe these channels originated as subglacial channels.
- An examination of the satellite imager over this area of Devon Island and on your Figure 8 reveals the flat lying bedrock stratigraphy of different tones/colors suggesting mesas. Are these visible on the Arctic DEM and could this natural stepped topography be an explanation for your erosional surfaces. The stepped topography indicates differential bedrock resistant to erosion, could resistance to erosion by different bedrock units also explain the slope breaks in the channeled areas, and a reason for the knickpoints within the channels? If so, is there any particular relevance to them other than they are frozen in time, and during the next glacial cycle their formation will resume with new flooding events? The Fig. 12 model is somewhat misleading for how you propose the erosional surfaces formed. Do the channels originate on a flat surface? In step ii) the implication is broad areal scouring to generate the surfaces. On Fig. 2 the scouring appears restricted to channel formation only. Placing your high resolution DEMs onto the regional DEM would help the viewer understand the surround topography better.
The reviewer raises a very interesting and pertinent question. We did not observe the steps between erosional surfaces to be associated with a change in lithology at any of the study sites discussed in this paper. The channels within each site are carved into the same dolomite unit (within the Allen Bay Fmn), which is thicker than the channel depth. To address this point, we will adopt Reviewer #2’s suggestion to overlay our high-resolution DEMs on the regional DEM and label the mesas in the Allen Bay Fmn to show that the ES’s are indeed very different morphologically and morphometrically.
To better show the uniform lithology, we present images from helicopter flights that exhibit the thickness of the Allen Bay Fmn to show that it is much thicker than the depth of the channels examined in this study and therefore the stepped topography does not originate from a change in stratigraphy. These images will be added to the supplementary information and some lines will be added in the main text to guide the reader.
The colourization of the ES in Figure 12 is purely to help the reader visualize each surface as it is incised by the flow(s) . To respond to the reviewer’s comment, we clarified in the caption following a helpful suggestion by Reviewer 3. The channels likely originated on a flat surface as the Arctic Platform is a relatively flat-lying sedimentary succession. Step ii) implies repeated overflow of the incipient channel that results in scouring of the adjacent bedrock which continues to erode and develop the scabland-type terrain we see in the labyrinthine channels. this area becomes progressively confined as the channel deepens and flow/flood events taper off or become less frequent, creating a second “layer” or erosional surface seen in Step iii).
- Section 5.2 is speculative considering that fluvial processes used as examples are from warm-based ice sheets (FIS), there doesn’t appear to be any modern fluvial activity in the study areas (ignoring melting from nivation hollows), and the slope breaks inside and outside the channels may well be a product of varying resistive properties of the flat-lying bedrock. This section could be shortened to one paragraph that lays out multiple working hypotheses for the slope breaks.
The authors will adopt Reviewer’s suggestion of shortening section 5.2 and will address the comment on slope breaks here and with the reviewer’s previous comment.
- There is a surprising lack of bedload within the channels, beyond a single mentioned of rounded cobbles (ln 273). Why might this be? Do ice-marginal channels contain bedload? Does the lack of bedload, which would be expected to be generated within a bedrock erosional channel, suggest stream power greater than the largest clasts that could form from eroded bedrock. What might a discharge hydrograph curve look like? Discharge estimates?
A recurring question about Devon Island’s meltwater channels is the location of the sedimentary deposits linked to channel incision. The three cobbles found were buried under cryofractured rock and had to be dug out – they were not part of a larger sedimentary deposit that was exposed or accessible. A follow-up field season will focus on searching for potential deposition centers within the channels via ground-penetrating radar and digging with proper tools.
The lack of exposed bedload, however, is not inconsistent with observations in landscapes modified by outburst floods.
The absence of accessible sedimentary deposits, follow-up sedimentological analyses and granulometry statistics on the median and maximum particle sizes potentially carried by the flow within these channels prevents us from quantitatively estimating discharge values at this point. However, using the cobble sizes (~10 cm) as absolute minimum sizes, we can derive an approximate minimum discharge assuming fluvial transport (subglacial transport and erosion would be expected to differ).
Minor comments:
- The abstract is very long.
We will adopt reviewer’s suggestion.
- Many instances of paragraphs and sentences beginning with ‘These’ or ‘Those’, and sometimes it is uncertain what is being referred to.
We will adopt reviewer’s suggestion.
- There is an inconsistent use of expressing range between two values. Use an en dash rather than hyphens, all with or without a space before and after. Similarly (Fig x) (Fig. x) (Figure x). (figure x)—be consistent.
We will adopt reviewer’s suggestion.
- Add spaces between numeral and unit (4 m).
We will adopt reviewer’s suggestion.
Specific Comments by Line Number.
Ln 13, 14, sentence topic is subglacial bedrock channels that is inconsistent with proglacial channels at end of sentence.
We will adopt reviewer’s suggestion.
Ln 22, place ‘subglacially’ in front of ‘by’.
We will adopt reviewer’s suggestion.
Ln 23, unclear what ‘these’ refers to, and remove capital L from ‘labyrinthine’.
We will adopt reviewer’s suggestion.
Ln 48, Grau Galofre et al. reference year is 2018 in references section, not 2022.
This comment brought up an issue with citation manager that has now been fixed. References section is now accurate.
Ln 56, other papers do not argue for time transgressive formation of tunnel channels (Fisher et al. 2022, 2023) in same area as Kehew worked.
This comment is noted by the authors.
Ln 75, hyphenation of cold to polythermal inconsistent within text. Superscript 14 for 14C, and since 100,000 14C years is well beyond limit of radiocarbon dating, perhaps just convert to 100 ka or use marine isotope stage numbers.
We will adopt reviewer’s suggestion.
Ln 78, provide reference for bedrock once in study area section, and not every time it’s mentioned at the different SG’s. Check capitalization of the rock units.
To avoid readers having to refer to previous subsections, the authors have decided to keep the references as is.
Ln 87, 88,100, 102: Acronym provided later for IIS, use after first instances, then for every subsequent time.
We will adopt reviewer’s suggestion.
Ln 97, statement about glacial landforms contradicts line 20 in abstract that there is a conspicuous lack of glacial landforms.
Ln 20 has been removed to improve clarity and length of the abstract.
Ln 112, 113, Dyke et al. 2002 and Simon et al. 2015 not included in reference list.
Issues with citation manager has been fixed and the reference list has been updated.
Ln 116, be specific about the glacial erosion features. Are they characteristic of a thawed or frozen bed.
We will adopt reviewer’s suggestion.
Ln 119, no year for Dyke ref. Who is ‘our’ for ‘our’ work reference? Just the authors on this paper?
We fixed the typo.
Ln 122, no clear what is meant by ‘soil’ is it not fine sediment, or do you mean regolith?
“Soil” has been removed as it is confusing in the context of an island with rare, localized vegetation.
Ln 125, is bedload an indicator between the two types of channels?
There is no evidence of deposition associated with any of the observed channels (both lateral and subglacial) so it is not clear what effect bedload had on channel morphology at this time.
Ln 144 missing word, or is ‘as’ to be ‘was’?
We will adopt reviewer’s suggestion.
Ln 145, Fig. 8B is out of order.
Changed (see section 4.4) to avoid confusion with figure chronology.
Ln 147, morphology and sedimentology of what? Sort of a repeat of previous sentence.
We will adopt reviewer’s suggestion.
Ln 154, is the UAV the same one as on line 149?
Yes, lines 149 and 154 have been swapped.
Ln 157, altitude of 100 m above channel bottom or plateau?
This has been clarified.
Ln 198, are channels only a meter wide?
This has been clarified. It should have read “metres wide” rather than “meter wide”.
Ln 201. Somewhat misleading to use sediment particle sizes for material not transported.
This is describing material that has been reworked by periglacial weathering. While not transported materials, the authors believe that the descriptors are necessary for context.
4.2 SG2, it’s interesting that the channels are curvy linear here. Is such a pattern expected subglacially, or more consistent with incision along a retreating ice margin?
This is an interesting feature of SG2. We suspect that this may be related to re-use of the existing subglacial channels as the ice margin retreated, although subglacial channels could increase their sinuosity near the margin (Schoof, 2010, supplementary information).
Ln 238, what does ‘loosely’ incised mean??
Should have been “shallowly”. This error has been fixed.
Ln 239, are not the marginal channels incised into bedrock? Sentence needs work as next phrase is confusing.
There are no visible bedrock slabs in the marginal channels we observed in field campaigns in 2016, 2017, and 2024, in stark contrast with the subglacial channels we traversed. Hence, we cannot say if the marginal channels are incised on bedrock or on cryofractured scree.
Ln 244, missing some words after ‘2024’
We will adopt reviewer’s suggestion.
Ln 248, include more information on the pothole in Fig. 4C. Dimensions etc.
We will adopt reviewer’s suggestion.
Ln 250, scabland is known to readers from the channeled scabland landscape first described by Bretz. Need to better introduce your use of the scabland word for bedrock slab scabland. Do the slabs have various meltwater sculpted forms on them to give the scab like appearance (grooves, cavettos, sichelwannen, rat tails, etc.)? Features not obvious on Fig 4. If high flow at onset is recorded by the bedrock slab in the bottom of the channel, then channel is pre-existing and little was accomplished by the water.
We will adopt reviewer’s suggestion. The word “scabland” here was used to describe exposed slabs of bedrock on the channel floor and walls at the headwaters, or sections where all topsoil or loose sediment had been removed. This word will be removed to improve clarity of this section and leave the “scabland” terminology to the appropriate discussion later in the paper. We did not observe any meltwater-sculpted forms on the slabs in the field, however this is something we will check again in upcoming field seasons to be sure.
Ln 279, here you say no channel deposition, but on line 273 you described rounded bedload.
The authors note some confusing wording around bedload in this instance – this is not bedload or a sedimentary deposit but rather three well-rounded cobbles that were found under a scree pavement layer within the channel floors. At the time of discovery, we did not have the resources to safely and effectively investigate further to confirm whether or not these cobbles were part of a larger deposit. This will be a focus of future field campaigns. The wording will be modified throughout the paper to ensure clarity.
Ln 293, comparison with hanging valleys is fine, but you have knickpoints or hanging channels, not valleys, in the study area, and throughout ms (e.g., ln 453).
We will adopt reviewer’s suggestion.
Ln 318, don’t see a Fig 6F.
This error has been fixed.
Ln341, ‘funnel-shaped origin’ is not a process but a morphological descriptor.
This section is meant to describe the morphology and sedimentology of SG3.
Ln 375, confusing how drainage can be in two opposite directions.
This will be clarified.
Ln 428, the lateral meltwater channels are difficult to see in Fig. 10E.
This will be modified for clarity and ease of identification of lateral meltwater channels.
Ln 461, see also Kehew et al., 2009 for example of larger anastomosing channels in sediment / weak bedrock.
The authors thank Reviewer #1 for this suggestion, this particular paper could not be located.
Ln 496, 531, terracing rather than layering would be a better description.
Since we compare the erosional surfaces to strath terraces later in the paper, layering may be better suited to avoid any confusion or pre-emptive interpretations of the surfaces.
Ln 502, 564, cobbles are not large bedload and are easily moved by small streams. Fig 10H does not exist.
We will adopt reviewer’s suggestion. The descriptor “well-rounded” was used to replace “large” to exemplify the flow energy required to round cobbles. “Fig. 10H” removed.
Ln 507. Considering that the remnant of the IIS (modern ice caps) are presumably cold based, subglacial floods events are more difficult to imagine especially with thinning ice. How does such an ice cap collapse? Any previous studies on this?
This is an interesting question we are still attempting to answer. The best estimate, as suggested in this paper and in Ruso et al. (2024), is that the flooding events are likely repeated events associated with occasional flooding that can occur under cold-based ice sheets if a subglacial reservoir is able to accumulate or fed by supraglacial lakes via conduits that open and close cyclically (accumulating pressure during frozen time periods). Ice sheet collapse or fast retreat can be associated with enhanced glacial hydrology, for example through the development of supraglacial lakes (e.g. East Antarctic Ice Sheet/Stokes et al 2019) or enhanced by flooding of a subglacial lake that creates a depression in the overlying ice (drawdown) and subsequently enhances formation of a supraglacial reservoir, reducing ice albedo (e.g., Burke et al., 2012). In the case of Devon Island, there are subglacial lakes currently under the modern Devon Ice Cap but to our knowledge there are no studies that focus on the dynamics and hydrology during the collapse/retreat of the IIS on the island.
Ln 538-540, confusing sentence.
We will adopt reviewer’s suggestion.
Ln 556, unclear what ‘their’ refers to. Lakes or channels?
The channels of the SGs. This has been clarified.
Ln 558, citation not in reference list.
This has been added.
Ln 564, cobbles and incision into bedrock is a weak argument for large discharge. Quantify by what you mean by large discharge. How have discharge calculations been made through the channels? What input data?
We have not performed at this stage paleodischarge calculations, owing to the very poor constraints on the sediment granulometry and maximum sizes carried by the water. The interpretations presented in this study are uniquely based on the available morphological data.
Ln566–569, unclear how a cold-based ice sheet over land would suddenly collapse. Moulins and crevasses reopening over same place seems reasonable if driven by subglacial topography. Similar channels are throughout surrounding region so presumably a common process operating.
We respectfully acknowledge this comment. More work, perhaps regional mapping specifically, will help elucidate these questions and bringing a clearer understanding to the collapse of the IIS on Devon Island to its current ice cap. We can address this by employing a more moderate use of the word “collapse” – using “retreat” more often instead to avoid a specific interpretation.
Figures:
Geographic grids (lat long, UTM) missing from all maps.
Figure 1. black text difficult to read in many places. Use a white line background to make more visible.
Figure 2, use a partially transparent arrow to indicate ice margin recession direction.
Figure 3 and most others, a large range in font sizes. Legend almost unreadable while the text in the symbology box is much too large.
Fig. 4A, white arrows are too faint.
Fig. 12B, the ice surface profile is very misleading.
We will adopt reviewer’s suggestions to improve all figures mentioned above.
Citation: https://doi.org/10.5194/egusphere-2025-5667-AC1
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AC1: 'Reply on RC1', Simona Ruso, 03 Apr 2026
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RC2: 'Comment on egusphere-2025-5667', Joel Gombiner, 25 Feb 2026
1. Overview
This paper maps and analyzes four bedrock channel networks in central Devon Island. The authors use digital elevation models and field observations to characterize the networks as anastomosing, overfit to the modern hydrological regime, and lacking in normal stream deposits, similar to the Channeled Scabland and the Antarctic Labyrinth. Adverse slopes along channel thalwegs and the presence of hanging valleys, together with the preceding observations and analogs, suggest the channels were eroded during subglacial meltwater floods from an expanded Devon Island Ice Cap or a regional Innuitian Ice Sheet.
This work contributes to a global literature on subglacially eroded bedrock channels, which are a widespread but relatively poorly understood landform across formerly glaciated areas on Earth and Mars. A key strength of the paper is the visualization of high-resolution DEMs, geomorphic mapping, and field photographs that will be useful for investigators working in analogous landscapes. The analysis is thoughtful and considers multiple possibilities of landscape development. Consideration of two additional processes might be helpful: One would be more clearly articulating the case for supraglacial reservoirs for some of the networks (as opposed to subglacial). The other would be considering palimpsest channel networks: for example could a surficial drainage network have first formed under a warmer, wetter climate via runoff on the gently sloping plateau, then later glaciation modified this dendritic network into an anastomosing one via both subglacial, and perhaps some proglacial, meltwater flooding.
Abstract
The abstract is a bit long and hard to follow. One step toward tightening the focus would be to move the background material about subglacial meltwater and erosion (lines 1 to 18) to the Introduction, placing more emphasis on methods and key results, with just enough context to understand the study.
2. Specific comments
Methods
The methods section focuses on data collection and processing, but it might be nice to break out analysis. The authors could start a section 3.3 called something like “Data Analysis” that describes how the mapping was done and how the interpretations were made. The text from 170 to 176 mostly serves this purpose as is, but it might help to put those lines under a separate section heading since they are not so much “Data Processing” as they are “Data Analysis”.
Sediment deposits
The text is focused on the channel morphology and topology, but some readers will be interested in the sedimentary deposits for understanding the nature of the channel-forming or -occupying events. Information on sediments is currently scattered throughout several sections. I see the benefit of associating information about deposits with the relevant channel network, but I would find the text more useful with something like a section 4.5 called “Sedimentary deposits” that captures in one place observations about the deposits associated with the channel networks, for example the rounded cobbles described on line 273 and the “recessive unit” on lines 370 to 375. This would help busy readers and might facilitate interpretations linking together the sedimentary features into a more cohesive picture.
Data availability
Data available upon request from author has a reputation for being an inconsistent way to access data. The authors should consider a data supplement that would include the geomorphic mapping results and other data such as field notes or morphological observations. This would facilitate follow-up studies to build upon the present work.
3. Technical Corrections
Body
Line 20: What are some examples of the typical glacial landforms you are indicating here? Subglacial channels are fairly typical glacial landforms so I am puzzled about the lack of typical landforms, especially given the statement on line 97.
Line 75: The radiocarbon timescale only goes back to about 50 ka, so I’m not sure what 100 14C ka BP means. You could consider converting all ages to ka using IntCal, and/or double check this reference to see what this age is.
Line 97. This contradicts the “conspicuous lack of glacial landforms” in the abstract.
Figure 1. The legend for 1C doesn’t match the figure caption. One is in ka BP and the other is in 14C BP. One is 11 to 14 and the other is 11 to 0.
Line 146-147. Does “lithology, grain size, scale, and morphology” refer to bedrock, deposits, or both? A separate note: tables summarizing these observational data might help the reader understand the results. Finally, this is the only place lithology is mentioned, and dolomite is the only rock type mentioned elsewhere in the text. What were the lithology data like and what was done with these data?
Line 155. Lidar is usually written as a common noun now. So this could be “lidar scans”.
Line 156. Digital elevation models would not typically be capitalized as they're not a proper noun (even though abbreviated as DEMs).
Line 251. Does “right at the onset” indicate onset of events in time, or onset in space (headwaters of the channel network).
Line 258. Does later refer to time or space?
Line 259. On what basis must the water have been sourced from top-down melting of the ice sheet?
Line 270. The morphology of the channel network should probably be described in present tense, since the network is still in place, so “deepened and widened” should become “deepens and widens”. Consistently using present tense when describing landscapes could be implemented throughout the text for consistency.
Line 273. How do you know the cobbles are “glaciofluvially reworked”? This would be stronger if you state the characteristics of the cobble deposit first and then make the interpretation about process.
Line 274. Does this discussion about sediment deposition in relation to subglacial channel networks only refer to SG2 or to all of the four networks analyzed?
Line 295. Global comment: sometimes there is a space after the ~ and sometimes not. I think the standard is ~1 m.
Line 479. The prior sentence talks specifically about channels on the Waterville Plateau associated with the Okanogan lobe, but it’s unclear if this sentence starting on line 479 discusses pro-glacial bedrock channel networks, i.e. the classic Channeled Scabland of the Cheney-Palouse and Telford-Crab Creek tracts, or the subglacial scabland on the Omak and Waterville Plateaus as mentioned in the prior sentence.
Line 502. Figure 10H showing the bedload cobbles seems to be missing.
Lines 520 to 542. Nice discussion of multiple levels of channels and anastomosis.
Line 553. The present text could reiterate the reasoning that meltwater was sourced from supraglacial reservoirs.
Figure 6B/6C. The y axis and axis fonts are too small to read.
References
Capitalization of titles should be consistent. Sentence case (first word and proper nouns capitalized) is a good option.
Line 695. Braun et al. (1999) has a DOI: https://doi.org/10.3189/172756499781821797
Line 698. Bretz (1923) has a DOI: https://doi.org/10.1130/GSAB-34-573
Line 706. Book title is missing the word “Edition” after fourth. Butterworth-Heinemann is the publisher, not the editor.
Line 709. Dalton et al. (2022) has a DOI. https://doi.org/10.1016/j.earscirev.2021.103875
Line 711. DOI is missing a 0. Correct DOI for Das et al. (2008) is https://doi.org/10.1126/science.1153360. Unclear what (1979) means next to the journal name.
Line 733. Howard et al. (1994) has a DOI. https://doi.org/10.1029/94JB00744
Line 741. Kamb (1970) has a DOI. https://doi.org/10.1029/RG008i004p00673
Line 745. Pine, Glaciers, and West should be capitalized in title.
Line 757. DOI does not work and it’s unclear if abstract actually has a DOI. Links to abstract on nasa.gov from Google Scholar were not working on 2/21/2025.
Line 775. Nienow et al. (1996) has a DOI. https://doi.org/10.1002/(SICI)1099-1085(199610)10:10%3C1411::AID-HYP470%3E3.0.CO;2-S
Line 778. Ó Cofaigh (1996) has a DOI. https://doi.org/10.1177/030913339602000101
Line 794. Shaw (2002) has a DOI. https://doi.org/10.1016/S1040-6182(01)00089-1
Line 801. The reference for Thorsteinsson and Mayr is incorrect. The suggested citation from Canada Department of Mines is as follows:
Thorsteinsson, R. & Mayr, U. (1987). The sedimentary rocks of Devon island, canadian arctic archipelago. Geological Survey of Canada, Memoir, 411, 182. Canada Department of Mines. https://doi.org/10.4095/122451
Line 806. Vandenberghe (1995) has a DOI. https://doi.org/10.1016/0277-3791(95)00043-O
Line 807. Van der Vegt et al. (2012) citation is incomplete. This is a chapter in a book called Glaciogenic Reservoirs and Hydrocarbon Systems with editors M. Huuse, J. Redfern, D. P. Le Heron, R. J. Dixon, A. Moscariello, J. Craig. The DOI is https://doi.org/10.1144/SP368.13
Line 815. I think the (1979) after the journal title is erroneous.
Citation: https://doi.org/10.5194/egusphere-2025-5667-RC2 -
AC2: 'Reply on RC2', Simona Ruso, 03 Apr 2026
Dear Reviewer #2,
We thank you for your insightful and helpful comments of our manuscript that will enhance the quality of our work. The following is a line-by-line response to your Referee Comments.
Abstract
The abstract is a bit long and hard to follow. One step toward tightening the focus would be to move the background material about subglacial meltwater and erosion (lines 1 to 18) to the Introduction, placing more emphasis on methods and key results, with just enough context to understand the study.
We will adopt reviewer’s suggestion.
- Specific comments
Methods
The methods section focuses on data collection and processing, but it might be nice to break out analysis. The authors could start a section 3.3 called something like “Data Analysis” that describes how the mapping was done and how the interpretations were made. The text from 170 to 176 mostly serves this purpose as is, but it might help to put those lines under a separate section heading since they are not so much “Data Processing” as they are “Data Analysis”.
We will adopt reviewer’s suggestion.
Sediment deposits
The text is focused on the channel morphology and topology, but some readers will be interested in the sedimentary deposits for understanding the nature of the channel-forming or -occupying events. Information on sediments is currently scattered throughout several sections. I see the benefit of associating information about deposits with the relevant channel network, but I would find the text more useful with something like a section 4.5 called “Sedimentary deposits” that captures in one place observations about the deposits associated with the channel networks, for example the rounded cobbles described on line 273 and the “recessive unit” on lines 370 to 375. This would help busy readers and might facilitate interpretations linking together the sedimentary features into a more cohesive picture.
We have not identified any exposed sedimentary deposits at or associated with our study sites. The rounded cobbles found in SG2 were dug up from under a cryofractured scree cover (with some difficulty), if a deposit exists it is buried under a > 30 cm layer of scree. At the time of discovery, we did not have the resources to safely and effectively investigate further to confirm whether or not these cobbles were part of a larger deposit, but this will be a focus of future field campaigns. Lines 273 and 370 – 375 will be modified in the paper to ensure clarity.
Data availability
Data available upon request from author has a reputation for being an inconsistent way to access data. The authors should consider a data supplement that would include the geomorphic mapping results and other data such as field notes or morphological observations. This would facilitate follow-up studies to build upon the present work.
The authors agree with Reviewer #2’s suggestion and will include supplementary information that includes extra field data and observations. LiDAR and UAV-derived data will be deposited into an accessible repository, such as Zenodo, and given a DOI.
- Technical Corrections
Body
Line 20: What are some examples of the typical glacial landforms you are indicating here? Subglacial channels are fairly typical glacial landforms so I am puzzled about the lack of typical landforms, especially given the statement on line 97.
This sentence has been removed to improve clarity and length of abstract.
Line 75: The radiocarbon timescale only goes back to about 50 ka, so I’m not sure what 100 14C ka BP means. You could consider converting all ages to ka using IntCal, and/or double check this reference to see what this age is.
This has been changed to 100 ka BP following suggestions from all reviewers. Radiocarbon ages (written as 14C) are only used throughout for dates more recent than 50ka following suggestions from previous reviewers of Ruso et al. 2024.
Line 97. This contradicts the “conspicuous lack of glacial landforms” in the abstract.
Line 20 has been removed.
Figure 1. The legend for 1C doesn’t match the figure caption. One is in ka BP and the other is in 14C BP. One is 11 to 14 and the other is 11 to 0.
This error has been fixed.
Line 146-147. Does “lithology, grain size, scale, and morphology” refer to bedrock, deposits, or both? A separate note: tables summarizing these observational data might help the reader understand the results. Finally, this is the only place lithology is mentioned, and dolomite is the only rock type mentioned elsewhere in the text. What were the lithology data like and what was done with these data?
This refers to bedrock – there are no clear depositional landforms associated with the subglacial channel networks. The only potential “depositional” feature is the boulder near the labyrinthine channels that may be a glacial erratic. Lithology of each study area is described in sections 4.1 to 4.4. observations of lithology were limited as SG1, 2 and 3 are incised into the same dolomite member of the Allen Bay formation.
Line 155. Lidar is usually written as a common noun now. So this could be “lidar scans”.
The authors respectfully note this comment.
Line 156. Digital elevation models would not typically be capitalized as they're not a proper noun (even though abbreviated as DEMs).
We will adopt reviewer’s suggestion.
Line 251. Does “right at the onset” indicate onset of events in time, or onset in space (headwaters of the channel network).
“Right at the onset” refers to the onset of events in time. This will be clarified.
Line 258. Does later refer to time or space?
Later in time. This will be clarified.
Line 259. On what basis must the water have been sourced from top-down melting of the ice sheet?
We do not observe landforms consistent with basal melting and the IIS has been recognised as largely cold-based, so we assume top-down melting of the ice sheet and/or release of englacial meltwater reservoirs.
Line 270. The morphology of the channel network should probably be described in present tense, since the network is still in place, so “deepened and widened” should become “deepens and widens”. Consistently using present tense when describing landscapes could be implemented throughout the text for consistency.
We will adopt reviewer’s suggestion.
Line 273. How do you know the cobbles are “glaciofluvially reworked”? This would be stronger if you state the characteristics of the cobble deposit first and then make the interpretation about process.
As per the “sediment deposits” comment above, the cobbles are not associated with a sedimentary deposit – they were dug out from the channel floor. This will be clarified throughout the text.
The interpretation that the cobbles were glaciofluvially reworked is because there is no evidence of fluvial erosion upstream or in connection with these channels that could have sourced the rounded cobbles. Since the channels have not been fluvially modified, we assume the last erosional regime was subglacial and therefore suggest glaciofluvial reworking of the cobbles found within the channel.
Line 274. Does this discussion about sediment deposition in relation to subglacial channel networks only refer to SG2 or to all of the four networks analyzed?
This specific discussion only refers to SG2. SG2 is the only network in which we found rounded cobbles.
Line 295. Global comment: sometimes there is a space after the ~ and sometimes not. I think the standard is ~1 m.
We will adopt reviewer’s suggestion.
Line 479. The prior sentence talks specifically about channels on the Waterville Plateau associated with the Okanogan lobe, but it’s unclear if this sentence starting on line 479 discusses pro-glacial bedrock channel networks, i.e. the classic Channeled Scabland of the Cheney-Palouse and Telford-Crab Creek tracts, or the subglacial scabland on the Omak and Waterville Plateaus as mentioned in the prior sentence.
This sentence discusses the subglacial scabland; this has been clarified.
Line 502. Figure 10H showing the bedload cobbles seems to be missing.
This figure was removed in an earlier revision and “Fig. 10H” should have been deleted from the text. This error has been fixed.
Lines 520 to 542. Nice discussion of multiple levels of channels and anastomosis.
The authors thank Reviewer 2 for this comment.
Line 553. The present text could reiterate the reasoning that meltwater was sourced from supraglacial reservoirs.
We will adopt reviewer’s suggestion.
Figure 6B/6C. The y axis and axis fonts are too small to read.
We will adopt reviewer’s suggestion to improve this figure.
References
We will adopt reviewer’s suggestions for all of the following comments to improve the reference list.
Capitalization of titles should be consistent. Sentence case (first word and proper nouns capitalized) is a good option.
Line 695. Braun et al. (1999) has a DOI: https://doi.org/10.3189/172756499781821797
Line 698. Bretz (1923) has a DOI: https://doi.org/10.1130/GSAB-34-573
Line 706. Book title is missing the word “Edition” after fourth. Butterworth-Heinemann is the publisher, not the editor.
Line 709. Dalton et al. (2022) has a DOI. https://doi.org/10.1016/j.earscirev.2021.103875
Line 711. DOI is missing a 0. Correct DOI for Das et al. (2008) is https://doi.org/10.1126/science.1153360. Unclear what (1979) means next to the journal name.
Line 733. Howard et al. (1994) has a DOI. https://doi.org/10.1029/94JB00744
Line 741. Kamb (1970) has a DOI. https://doi.org/10.1029/RG008i004p00673
Line 745. Pine, Glaciers, and West should be capitalized in title.
Line 757. DOI does not work and it’s unclear if abstract actually has a DOI. Links to abstract on nasa.gov from Google Scholar were not working on 2/21/2025.
Line 775. Nienow et al. (1996) has a DOI. https://doi.org/10.1002/(SICI)1099-1085(199610)10:10%3C1411::AID-HYP470%3E3.0.CO;2-S
Line 778. Ó Cofaigh (1996) has a DOI. https://doi.org/10.1177/030913339602000101
Line 794. Shaw (2002) has a DOI. https://doi.org/10.1016/S1040-6182(01)00089-1
Line 801. The reference for Thorsteinsson and Mayr is incorrect. The suggested citation from Canada Department of Mines is as follows:
Thorsteinsson, R. & Mayr, U. (1987). The sedimentary rocks of Devon island, canadian arctic archipelago. Geological Survey of Canada, Memoir, 411, 182. Canada Department of Mines. https://doi.org/10.4095/122451
Line 806. Vandenberghe (1995) has a DOI. https://doi.org/10.1016/0277-3791(95)00043-O
Line 807. Van der Vegt et al. (2012) citation is incomplete. This is a chapter in a book called Glaciogenic Reservoirs and Hydrocarbon Systems with editors M. Huuse, J. Redfern, D. P. Le Heron, R. J. Dixon, A. Moscariello, J. Craig. The DOI is https://doi.org/10.1144/SP368.13
Line 815. I think the (1979) after the journal title is erroneous.
Citation: https://doi.org/10.5194/egusphere-2025-5667-AC2
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AC2: 'Reply on RC2', Simona Ruso, 03 Apr 2026
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RC3: 'Comment on egusphere-2025-5667', Anonymous Referee #3, 09 Mar 2026
The manuscript of Ruso et al. expands on previous work of the same team from the same localities (Grau Galofre et al. 2018, The Cryosphere; Ruso et al., 2024), and it is thus a third manuscript based on a relatively small set of landforms. This manuscript adds a new site ‘the Labyrinth’, called after and compared to the set of landforms described in Antarctica by David Sugden in the 1990s. The landform sets SG1 and SG2 (described in Grau Galofre et al., 2018) were interpreted by Ruso et al. (2024) as likely stemming from ‘episodic but locally intense drainage of supraglacial meltwater’. In this manuscript, the landform set ‘Devon Island Labyrinth’ is speculated to have possibly formed by floods from a subglacial lake (the location of which might have been in its close vicinity). The sets SG1 and SG2 are not clearly reinterpreted from the supraglacial lake drainage origin, but the manuscript states that channel anastomosis and slope breaks within the landform sets SG1, SG2, and the labyrinth indicate ‘short-lived, locally intense episodes of subglacial flood erosion’, with comparisons made to the recently inferred subglacial floods in the Okanogan lobe of the Cordilleran Ice Sheet (Gombiner and Lesemann, 2024).
The topic covered is of interest for broader readership of TC due to possible analogs with the studied meltwater dynamics in Greenland and Antarctica. However, in its present form, the text of the manuscript is quite difficult to read and would benefit from further work on the style. I offer a couple of major comments below, followed by a list of minor comments ordered by their line numbers.
Major comments:
The channel morphology descriptions feel possibly too extensive for the main text. The authors might explore other options to retain the information needed for the inferences they make that would allow for shortening the results section of the manuscript.
In the discussion section, the authors should make sure that any possible change of interpretation compared to their earlier work in the same area is more clearly explained and properly argued for.
Minor comments:
‘Labyrinthine’ - small case or capital L?
Abstract: shorten, try to make the text more fluent, it doesn’t read very well in its current form.
L 45 ‘effectively increase effective pressure’ can you rephrase so that it reads better?
L 54 Unclear why tunnel valleys are suddenly mentioned here: this term is somewhat problematic due its unclear formation processes and does not simply link to the channelized/distributed drainage dichotomy described above. Maybe move this sentence after you introduce N channels in the next para.
L 62 Is ‘mega’ needed there?
L 75 ‘during the last ~100 14C ka BP’ cannot you simply write ‘the last 100 ka’? Writing it in radiocarbon years is nonsense because that dating method only reaches to about 45 thousand years. BP also not needed because if you were referring to other 100 thousand year period, you would use kyr instead of ka.
L 76 ‘around our study region’ you haven’t introduced your study region yet, so this geographic localization does not really work.
L 98 You list ‘ice marginal and subglacial drainage pathways’ as an example of landform record. But these are interpretations and not standard terms in glacial geomorphological terminology. It’s perfectly fine to make these assumptions later, but here, in connection to landform record, stick to standard landform terminology.
L 102-103 ‘…cycles of advance and retreat from 115 – 25 ka’ From doesn’t work here. Between fits better.
L 104 If you mention modelling specifically, then refer directly to numerical modelling studies, in addition to the review of Dalton et al. (2022). Is this sourced from Stokes et al. (2012, QSR)?
L106-109 what time period are the min max glaciation scenarios meant for? Is there really such uncertainty for the LGM?
L 110-115 The wording ‘glaciochronological and geomorphological modeling’ is confusing, I would suggest to keep the term ‘modeling’ for truly numerical models. You should also be consistent in the spelling of the word: elsewhere you write it with double L.
L 116 This conflicts with you previous statement of ‘remarkably well-preserved record of glacial and subglacial landforms’.
L 123 maybe rather ‘valley slopes’?
L 138 Introduce the ATV abbreviation
L 144 ‘was’ instead of ‘as’
L 154 No need to spell out and reintroduce the UAV abbreviation, you’ve done that above
L 244 delete the definite article before 2024
Fig. 6 caption: ‘red box’ is not a box. ‘Red polygon’ instead?
Fig. 12 It doesn’t make sense to have the ground layered into three units already in the first and second pair of panels. If you are to describe erosional surfaces, then these are cut into one and the same ground, that should be drawn in one colour shade. The way you depict it makes it look like each flood event erodes into a different lithological/stratigraphic unit.
L 560-563 Long sentence. Can you cut it in two to make it easier to read?
L 574 cross-divide channels are not marked (and are difficult/impossible to see) in Fig. 8A.
L 574-576 While I’m not saying this is the case here, larger proglacial lakes commonly go through a series of different outlets that are controlled by GIA rebound in response to changing ice sheet loading. Your statement thus cannot be phrased as a general rule.
Citation: https://doi.org/10.5194/egusphere-2025-5667-RC3 -
AC3: 'Reply on RC3', Simona Ruso, 03 Apr 2026
Dear Reviewer #3,
We thank you for your insightful and helpful comments of our manuscript that will enhance the quality of our work. The following is a line-by-line response to your Referee Comments.
Major comments:
The channel morphology descriptions feel possibly too extensive for the main text. The authors might explore other options to retain the information needed for the inferences they make that would allow for shortening the results section of the manuscript.
The authors will streamline this text and refer the reader to our previous work for more detailed descriptions/discussions where possible.
In the discussion section, the authors should make sure that any possible change of interpretation compared to their earlier work in the same area is more clearly explained and properly argued for.
At this point, we have not changed our earlier interpretations; rather we have built on them and recognized new features that are discussed in this paper. We will clarify this point in the discussion section.
Minor comments:
‘Labyrinthine’ - small case or capital L?
This error has been fixed.
Abstract: shorten, try to make the text more fluent, it doesn’t read very well in its current form.
We will adopt reviewer’s suggestion.
L 45 ‘effectively increase effective pressure’ can you rephrase so that it reads better?
We will adopt reviewer’s suggestion.
L 54 Unclear why tunnel valleys are suddenly mentioned here: this term is somewhat problematic due its unclear formation processes and does not simply link to the channelized/distributed drainage dichotomy described above. Maybe move this sentence after you introduce N channels in the next para.
We will adopt reviewer’s suggestion.
L 62 Is ‘mega’ needed there?
We believe ‘mega’ is needed here to distinguish from specific flood theories that involve significant, large-scale (“mega”) flooding events such as Shaw’s (2002) mega-flood hypothesis.
L 75 ‘during the last ~100 14C ka BP’ cannot you simply write ‘the last 100 ka’? Writing it in radiocarbon years is nonsense because that dating method only reaches to about 45 thousand years. BP also not needed because if you were referring to other 100 thousand year period, you would use kyr instead of ka.
This has been changed to 100 ka BP following suggestions from all reviewers. Radiocarbon ages (written as 14C) are only used throughout for dates more recent than 50ka following suggestions from previous reviewers of Ruso et al. 2024.
L 76 ‘around our study region’ you haven’t introduced your study region yet, so this geographic localization does not really work.
This will be rephrased.
L 98 You list ‘ice marginal and subglacial drainage pathways’ as an example of landform record. But these are interpretations and not standard terms in glacial geomorphological terminology. It’s perfectly fine to make these assumptions later, but here, in connection to landform record, stick to standard landform terminology.
These are not interpretations conceived in this paper, rather this is terminology commonly used to describe the landscape of Devon Island established by researchers in the 1990’s.
L 102-103 ‘…cycles of advance and retreat from 115 – 25 ka’ From doesn’t work here. Between fits better.
We will adopt reviewer’s suggestion.
L 104 If you mention modelling specifically, then refer directly to numerical modelling studies, in addition to the review of Dalton et al. (2022). Is this sourced from Stokes et al. (2012, QSR)?
This refers to the review of Dalton et al. (2022) that uses data from Stokes et al. (2012). We will adopt reviewer’s suggestion. We will be more moderate with our use of “modelling” and replace throughout with an appropriate term.
L106-109 what time period are the min max glaciation scenarios meant for? Is there really such uncertainty for the LGM?
These scenarios are for the Last Glacial Maximum. There is significant uncertainty specifically for the IIS, due to a lack of dates from the island with the except of marine shells along the coast dated in the 1990’s (Dyke’s body of work, England et al). Cosmogenic nuclide (exposure) dating of Devon Island was carried out for the first time using samples collected from our 2024 field campaign (Andres Escorihuela et al., in preparation) – these data will certainly provide a clearer understanding of ice retreat on the island. There is lots of data for the Laurentide Ice Sheet but very little precise time constraints and predicted ice margins for the IIS in the QEI, as most modelling focusses on the Laurentide while the IIS is more of an auxiliary data point (e.g., Dalton et al., 2022).
L 110-115 The wording ‘glaciochronological and geomorphological modeling’ is confusing, I would suggest to keep the term ‘modeling’ for truly numerical models. You should also be consistent in the spelling of the word: elsewhere you write it with double L.
We will adopt reviewer’s suggestions.
L 116 This conflicts with you previous statement of ‘remarkably well-preserved record of glacial and subglacial landforms’.
We note the confusing wording here – this will be clarified in the text. What landforms are present on Devon Island are exceptionally well-preserved owing to the lack of precipitation and vegetative cover.
L 123 maybe rather ‘valley slopes’?
We will adopt reviewer’s suggestion.
L 138 Introduce the ATV abbreviation
We will adopt reviewer’s suggestion.
L 144 ‘was’ instead of ‘as’
We will adopt reviewer’s suggestion.
L 154 No need to spell out and reintroduce the UAV abbreviation, you’ve done that above
Lines 149 and 154 have been swapped for clarity following suggestions by Reviewer 1.
L 244 delete the definite article before 2024
This line was missing words at the end of the sentence as noted by Reviewer 1. This error has been fixed.
Fig. 6 caption: ‘red box’ is not a box. ‘Red polygon’ instead?
We will adopt reviewer’s suggestion.
Fig. 12 It doesn’t make sense to have the ground layered into three units already in the first and second pair of panels. If you are to describe erosional surfaces, then these are cut into one and the same ground, that should be drawn in one colour shade. The way you depict it makes it look like each flood event erodes into a different lithological/stratigraphic unit.
The colours are to help the reader visualize the different erosional surfaces as they are incised by the flow(s). The author’s note the confusion this may present here in terms of lithological units. A sentence has been added in the figure caption for clarity.
L 560-563 Long sentence. Can you cut it in two to make it easier to read?
We will adopt reviewer’s suggestion.
L 574 cross-divide channels are not marked (and are difficult/impossible to see) in Fig. 8A.
We will adopt reviewer’s suggestion to improve this figure.
L 574-576 While I’m not saying this is the case here, larger proglacial lakes commonly go through a series of different outlets that are controlled by GIA rebound in response to changing ice sheet loading. Your statement thus cannot be phrased as a general rule.
We will adopt reviewer’s suggestion to avoid phrasing this statement as a rule.
Citation: https://doi.org/10.5194/egusphere-2025-5667-AC3
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AC3: 'Reply on RC3', Simona Ruso, 03 Apr 2026
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The manuscript by Ruso et al. is an intriguing look at channel networks on Devon Island. The paper begins with a solid review of the literature on subglacial meltwater and channels, folding in proglacial examples with similar morphology to their study site. There is a variety of interesting and detailed measurements of the channels with limited ground truthing. The distinction between ice-marginal vs. subglacial channels could be stronger, and the text could be written more efficiently by deleting much of the commentary. Lastly, there could be more discussion on the longitudinal profiles and whether they make the case for a subglacial origin for the channels. Abstract is quite long and the text is very wordy with too much commentary and use of personal pronouns, in my opinion.
Major comments
Minor comments:
Specific Comments by Line Number.
Ln 13, 14, sentence topic is subglacial bedrock channels that is inconsistent with proglacial channels at end of sentence.
Ln 22, place ‘subglacially’ in front of ‘by’.
Ln 23, unclear what ‘these’ refers to, and remove capital L from ‘labyrinthine’.
Ln 48, Grau Galofre et al. reference year is 2018 in references section, not 2022.
Ln 56, other papers do not argue for time transgressive formation of tunnel channels (Fisher et al. 2022, 2023) in same area as Kehew worked.
Ln 75, hyphenation of cold to polythermal inconsistent within text. Superscript 14 for 14C, and since 100,000 14C years is well beyond limit of radiocarbon dating, perhaps just convert to 100 ka or use marine isotope stage numbers.
Ln 78, provide reference for bedrock once in study area section, and not every time it’s mentioned at the different SG’s. Check capitalization of the rock units.
Ln 87, 88,100, 102: Acronym provided later for IIS, use after first instances, then for every subsequent time.
Ln 97, statement about glacial landforms contradicts line 20 in abstract that there is a conspicuous lack of glacial landforms.
Ln 112, 113, Dyke et al. 2002 and Simon et al. 2015 not included in reference list.
Ln 116, be specific about the glacial erosion features. Are they characteristic of a thawed or frozen bed.
Ln 119, no year for Dyke ref. Who is ‘our’ for ‘our’ work reference? Just the authors on this paper?
Ln 122, no clear what is meant by ‘soil’ is it not fine sediment, or do you mean regolith?
Ln 125, is bedload an indicator between the two types of channels?
Ln 144 missing word, or is ‘as’ to be ‘was’?
Ln 145, Fig. 8B is out of order.
Ln 147, morphology and sedimentology of what? Sort of a repeat of previous sentence.
Ln 154, is the UAV the same one as on line 149?
Ln 157, altitude of 100 m above channel bottom or plateau?
Ln 198, are channels only a meter wide?
Ln 201. Somewhat misleading to use sediment particle sizes for material not transported.
4.2 SG2, it’s interesting that the channels are curvy linear here. Is such a pattern expected subglacially, or more consistent with incision along a retreating ice margin?
Ln 238, what does ‘loosely’ incised mean??
Ln 239, are not the marginal channels incised into bedrock? Sentence needs work as next phrase is confusing.
Ln 244, missing some words after ‘2024’
Ln 248, include more information on the pothole in Fig. 4C. Dimensions etc.
Ln 250, scabland is known to readers from the channeled scabland landscape first described by Bretz. Need to better introduce your use of the scabland word for bedrock slab scabland. Do the slabs have various meltwater sculpted forms on them to give the scab like appearance (grooves, cavettos, sichelwannen, rat tails, etc.)? Features not obvious on Fig 4. If high flow at onset is recorded by the bedrock slab in the bottom of the channel, then channel is pre-existing and little was accomplished by the water.
Ln 279, here you say no channel deposition, but on line 273 you described rounded bedload.
Ln 293, comparison with hanging valleys is fine, but you have knickpoints or hanging channels, not valleys, in the study area, and throughout ms (e.g., ln 453).
Ln 318, don’t see a Fig 6F.
Ln341, ‘funnel-shaped origin’ is not a process but a morphological descriptor.
Ln 375, confusing how drainage can be in two opposite directions.
Ln 428, the lateral meltwater channels are difficult to see in Fig. 10E.
Ln 461, see also Kehew et al., 2009 for example of larger anastomosing channels in sediment / weak bedrock.
Ln 496, 531, terracing rather than layering would be a better description.
Ln 502, 564, cobbles are not large bedload and are easily moved by small streams. Fig 10H does not exist.
Ln 507. Considering that the remnant of the IIS (modern ice caps) are presumably cold based, subglacial floods events are more difficult to imagine especially with thinning ice. How does such an ice cap collapse? Any previous studies on this?
Ln 538-540, confusing sentence.
Ln 556, unclear what ‘their’ refers to. Lakes or channels?
Ln 558, citation not in reference list.
Ln 564, cobbles and incision into bedrock is a weak argument for large discharge. Quantify by what you mean by large discharge. How have discharge calculations been made through the channels? What input data?
Ln566–569, unclear how a cold-based ice sheet over land would suddenly collapse. Moulins and crevasses reopening over same place seems reasonable if driven by subglacial topography. Similar channels are throughout surrounding region so presumably a common process operating.
Figures:
Geographic grids (lat long, UTM) missing from all maps.
Figure 1. black text difficult to read in many places. Use a white line background to make more visible.
Figure 2, use a partially transparent arrow to indicate ice margin recession direction.
Figure 3 and most others, a large range in font sizes. Legend almost unreadable while the text in the symbology box is much too large.
Fig. 4A, white arrows are too faint.
Fig. 12B, the ice surface profile is very misleading.